The present invention is directed to a golf ball and, more particularly, a golf ball having an improved dimple pattern.
Golf balls were originally made with smooth outer surfaces. In the late nineteenth century, players observed that the guttie golf balls travelled further as they got older and more gouged up. The players then began to roughen the surface of new golf balls with a hammer to increase flight distance. Manufacturers soon caught on and began molding non-smooth outer surfaces on golf balls.
By the mid 1900""s, almost every golf ball being made had 336 dimples arranged in an octahedral pattern. Generally, these balls had about 60% of their outer surface covered by dimples. In 1983, Titleist introduced the TITLEIST 384, which, not surprisingly, had 384 dimples that were arranged in an icosahedral pattern. About 76% of its outer surface was covered with dimples. Today""s dimpled golf balls travel nearly two times farther than a similar ball without dimples.
There have also been many patents directed to various dimple patterns. U.S. Pat. No. 4,560,168, which issued to the present inventor, is directed to an icosahedron pattern with six great circles that do not intersect any dimples. The pattern is similar to the present invention in that it has the triangular regions of the icosahedron pattern. However, this type of pattern provided a relatively low surface area coverage, i.e., less than 75% of the outer surface is covered by dimples.
The dimples on a golf ball are important in reducing drag and increasing lift. Drag is the air resistance that acts on the golf ball in the opposite direction from the balls flight direction. As the ball travels through the air, the air surrounding the ball has different velocities and, thus, different pressures. The air exerts maximum pressure at the stagnation point on the front of the ball. The air then flows over the sides of the ball and has increased velocity and reduced pressure. At some point it separates from the surface of the ball, leaving a large turbulent flow area called the wake that has low pressure. The difference in the high pressure in front of the ball and the low pressure behind the ball slows the ball down. This is the primary source of drag for a golf ball.
The dimples on the ball create a turbulent boundary layer around the ball, i.e., the air in a thin layer adjacent to the ball flows in a turbulent manner. The turbulence energizes the boundary layer and helps it stay attached further around the ball to reduce the area of the wake. This greatly increases the pressure behind the ball and substantially reduces the drag.
Lift is the upward force on the ball that is created from a difference in pressure on the top of the ball to the bottom of the ball. The difference in pressure is created by a warpage in the air flow resulting from the ball""s back spin. Due to the back spin, the top of the ball moves with the air flow, which delays the separation to a point further aft. Conversely, the bottom of the ball moves against the air flow, moving the separation point forward. This asymmetrical separation creates an arch in the flow pattern, requiring the air over the top of the ball to move faster, and thus have lower pressure than the air underneath the ball.
Almost every golf ball manufacturer researches dimple patterns in order to increase the distance travelled by a golf ball. A high degree of dimple coverage is beneficial to flight distance, but only if the dimples are of a reasonable size. Dimple coverage gained by filling spaces with tiny dimples is not very effective, since tiny dimples are not good turbulence generators. Most balls today still have many large spaces between dimples or have filled in these spaces with very small dimples that do not create enough turbulence at average golf ball velocities.
The present invention is directed to a golf ball dimple pattern that provides a surprisingly better dimple packing than any previous pattern so that a greater percentage of the surface of the golf ball is covered by dimples. The prior art golf balls have dimple patterns that leave many large spaces between adjacent dimples and/or use small dimples to fill in the spaces. The golf balls according to the present invention have triangular regions with a plurality of dimple sizes arranged to provide a remarkably high percentage of dimple coverage while avoiding groupings of relatively large dimples.
The triangular regions have a first set of dimples formed in a large triangle and a second set of dimples formed in a small triangle inside of and adjacent to the large triangle. The first set of dimples forming the large triangle comprises dimples that increase in size from the dimples on the points of the triangle toward the midpoint of the triangle side. Thus, the dimples close to or on the midpoint of the sides of the triangle are the largest dimples on the large triangle. Each dimple diameter along the triangle side is equal to or greater than the adjacent dimple toward the vertex or triangle point. Through this layout and with proper sizing, as set forth below, the dimple coverage is greater than 80% of the surface of the golf ball.
Further, the dimples are arranged so that there are three or less great circle paths that do not intersect any dimples to minimize undimpled surface area. Great circles take up a significant amount of the surface area and an intersection of more than two great circles creates very small angles that have to be filled with very small dimples or large gaps are created.
Still further, the dimples are arranged such that there are no more than two adjacent dimples of the largest diameter. Thus, the largest dimples are more evenly spaced over the ball and are not clumped together.
The golf balls according to the present invention have dimples that cover more than 80% of the outer surface. More importantly, the dimple coverage is not accomplished by the mere addition of very small dimples that do not effectively contribute to the creation of turbulence. Preferably, the total number of dimples is about 300 to about 500 and at least about 80% of the dimples have a diameter of about 0.11 inches or greater. More preferably, at least about 90% of the dimples have a diameter of about 0.11 inches or greater. Most preferably, at least about 95% of the dimples have a diameter of about 0.11 inches or greater.
The first embodiment of the present invention is a golf ball having an icosahedron dimple pattern. The pattern comprises 20 triangles made from about 362 dimples and does not have a great circle that does not intersect any dimples. Each of the large triangles, preferably, has an odd number of dimples (7) along each side and the small triangles have an even number of dimples (4) along each side. To properly pack the dimples, the large triangle has nine more dimples than the small triangle. In the first embodiment, the ball has five different sizes of dimples in total. The sides of the large triangle have four different sizes of dimples and the small triangles have two different sizes of dimples.
The second embodiment of the present invention is a golf ball also having an icosahedron dimple pattern. The pattern is substantially similar to the first embodiment, but the large triangle is comprised of three different sizes of dimples and the small triangles have only one size of dimple. In the second embodiment, there are 392 dimples and one great circle that does not intersect any dimples.
The third embodiment of the present invention is a golf ball having an octahedron dimple pattern. The pattern comprises eight triangles made from about 440 dimples and has three great circles that do not intersect any dimples.
In the octahedron pattern, the pattern comprises a third set of dimples formed in a smallest triangle inside of and adjacent to the small triangle. To properly pack the dimples, the large triangle has nine more dimples than the small triangle and the small triangle has nine more dimples than the smallest triangle. In this embodiment, the ball has six different dimple sizes distributed over the surface of the ball. The large triangle has five different dimple sizes, the small triangle has three different dimple sizes and the smallest triangle has two different dimple sizes.